The invention relates to a picture pick-up device including a solid-state sensor and operating with signal interference reduction. The sensor comprises a picture pick-up member and a first and second shift register member, the picture pick-up member being formed with picture pick-up elements which are sensitive to picture information from a scene to be recorded, each shift register member, which is controllable by clock pulse signals, being formed with at least one parallel-in, series-out shift register having a controllable parallel input coupling with the picture pick-up elements. The first shift register member has a series output coupling with a first output of the sensor and the second shift register member has a series output coupling with a second output of the sensor, the first and second outputs of the sensor supplying a signal with picture information and interference and a signal with interference only, respectively, by means of the clock pulse control of the shift register members, the picture pick-up device for obtaining the interference reduction further including a differential amplifier having a non-inverting and an inverting input coupled to the first and the second output, respectively, of the sensor, and an output for the supply of a signal with picture information and reduced interference.
A picture pick-up device of this type is described in U.S. Pat. No. 4,490,744, more specifically in the form of a sensor having photosensitive picture pick-up elements. Furthermore, the sensor is in the form of a charge transfer device, more specifically a frame transfer device. The picture pick-up member is coupled via a storage member to the parallel inputs of the first shift register member, and the second shift register member is present on the opposite side of the picture pick-up member. The storage member and the shift register members are shielded from light. In the picture pick-up member, and the storage member the picture pick-up elements and storage elements, respectively, are arranged in rows and columns.
If the picture pick-up device operates as a television camera, the patent describes that for the purpose of generating signals, the picture information obtained in the picture pick-up member after a light integration period is transferred to the storage member upon commencement of a television field blanking period. Subsequently, the parallel transfer of the then "empty" picture pick-up member to the second shift register member is effected which thereby only receives signal smear in the form of a signal interference which is then read to the second output of the sensor. A memory device having a circulation time of one television line period is connected to the second sensor output. Instead of the memory device with the circulation, the patent also states the use of a digital random access memory. An output of the memory device with the signal conveying smear and delayed over one line period is coupled to the inverting input of the differential amplifier whose non-inverting input is connected to the first sensor output conveying the signal with picture information and smear. The coupling between the memory device and the differential amplifier comprises a gating circuit which is controlled via a threshold circuit from the signal conveying the picture information and the smear.
It is apparent that the smear is added columnwise once per field period and is subsequently utilized several times for the smear reduction during the line periods of the field period. This requires the line period memory device to be used in co-operation with the gating circuit and the threshold circuit.